How-To Guide

Table Of Contents
R01UH0823EJ0110 Rev.1.10 Page 892 of 1852
Nov 30, 2020
RX23W Group 32. USB 2.0 Host/Function Module (USBc)
32.2.18 Frame Number Register (FRMNUM)
Note 1. To clear the status, write 0 only to the bits to be cleared; write 1 to the other bits.
FRNM[10:0] Flags (Frame Number Flag)
These bits indicate the latest frame number for the USB after the issuing of an SOF packet every 1 ms or writing to the
FRNM[10:0] flags at the SOF packet reception.
CRCE Flag (Receive Data Error Flag)
Indicates whether a CRC error or bit stuffing error has been detected in the pipe during isochronous transfer.
The CRCE flag can be set to 0 by writing 0 to the CRCE flag by software. Here, 1 should be written to the other bits in
FRMNUM.
On detecting a CRC error, the USB generates the internal NRDY interrupt request.
OVRN Flag (Overrun/Underrun Detection Status Flag)
Indicates whether an overrun/underrun error has been detected in the pipe during isochronous transfer.
The OVRN flag can be set to 0 by writing 0 to the OVRN flag by software. Here, 1 should be written to the other bits in
FRMNUM.
(1) When the host controller is selected
The USB sets the OVRN flag to 1 on any of the following conditions.
For the isochronous transfer pipe in the transmitting direction, the time to issue an OUT token comes before all the
transmit data has been written to the FIFO buffer.
For the isochronous transfer pipe in the receiving direction, the time to issue an IN token comes when no FIFO
buffer planes are empty.
(2) When the function controller is selected
The USB sets the OVRN flag to 1 on any of the following conditions.
For the isochronous transfer pipe in the transmitting direction, the IN token is received before all the transmit data
has been written to the FIFO buffer.
For the isochronous transfer pipe in the receiving direction, the OUT token is received when no FIFO buffer planes
are empty.
Address(es): USB0.FRMNUM 000A 004Ch
b15 b14 b13 b12 b11 b10 b9 b8 b7 b6 b5 b4 b3 b2 b1 b0
OVRN CRCE FRNM[10:0]
Value after reset:
0000000000000000
Bit Symbol Bit Name Description R/W
b10 to b0 FRNM[10:0] Frame Number Flag Latest frame number R
b13 to b11 Reserved These bits are read as 0. The write value should be 0. R/W
b14 CRCE Receive Data Error Flag 0: No error
1: An error occurred
R/W
*1
b15 OVRN Overrun/Underrun Detection Status
Flag
0: No error
1: An error occurred
R/W
*1